When an electronic circuit is turned on, in order to prevent an inrush current that may negatively impact an input DC-bus voltage, a soft-start circuit will usually be included in the electronic circuit to control the inrush current to stay below a reasonable threshold value.
Typically, a soft-start circuit consists of a field-effect transistor and a slow start control circuit. The slow start control circuit controls a rate of increase in the voltage between the gate and the source (GS) of the field-effect transistor so as to slowly switch on the field-effect transistor, thereby suppressing an inrush current that may otherwise occur instantaneously when the power supply voltage is applied to the electronic circuit.
Conventional soft-start circuits constructed from discrete components may work well the first time they are turned on. However, after these conventional soft-start circuits are turned off, they may require a relatively long time period before they reset completely. If the time interval between the power supply being turned off and the power supply being turned on again is relatively short, then, when the power supply is turned on again, the soft-start circuit may not work properly, as the inrush current may exceed a set threshold value and this may lead to unpredictable consequences.